柳江流域不同水文季节水质对附生硅藻群落的影响研究

为研究溶解氧(DO)、化学需氧量(CODMn)、氨氮(NH4+-N)、汞(Hg)、铅(Pb)、砷(As)和镉(Cd)在枯水期和丰水期变化对附生硅藻群落结构的影响, 分别于 2017 年 3 月和 6 月对柳江流域进行了调查分析, 旨在为深入研究柳江流域硅藻群落分布特征奠定基础, 以期为该流域水质的利用和管理提供理论依据。柳江流域共鉴定出附生硅藻 137 种, 隶属于 6 目 9 科 34 属。各采样点硅藻丰富度变化范围为 13-42 种, 呈现为丰水期高于枯水期。硅藻优势种组成在枯、丰水期分别有 5 种和 8 种, 具有明显的季节演替。聚类分析(Cluster analysis)显示, 硅藻群落结构在时空分布上存在差异, 枯水期可分为 3 个类群, 基本呈现在干流及支流段的上游、中游和下游; 丰水期可分为 2 个类群, 大致分布在流域的中下游和上游。其中, 在枯水期, Cyclotella fottii、Cyclotella. stelligera、Achnanthes minutissima 和 Cymbella laveis 在上游为优势种, A. minutissima 和 Nitzschia valdecostata 在中游丰度较高, 下游优势种为 Navicula cryptocephala、Amphora montana 和 A. minutissima 等; 在丰水期, 中下游优势种主要以 Nitzschia palea 为主, 上游优势种为 A. minutissima、A. montana 和 Achnanthes petersenii 等。主成分分析(Principle component analysis, PCA)和冗余分析(Redundancy analysis, RDA)显示, 枯水期水质因子对硅藻群落的影响为 Pb>Cd>Hg>As>CODMn>DO, 丰水期为 As>DO>CODMn>NH4+-N>Cd。结果表明, 水质因子 Cd、As、DO 和 CODMn 在枯水期和丰水期都对硅藻群落结构的变化起着重要作用, 但重金属因子在枯水期对硅藻影响较大, 而溶解氧在丰水期对硅藻影响较大。

The effects of water quality on epilithic diatom community in different hydrological seasons in Liujiang River Basin

To study the effects of changes in seven water quality factors(Dissolved oxygen,DO;Chemical oxygen demand,CODMn;Ammonia nitrogen,NH4+-N;Mercury,Hg;Plumbum,Pb;Arsenic,As;Cadmium,Cd)during the dry and wet seasons on the community structure of epilithic diatoms,we conducted investigations in March and June 2017 respectively in the Liujiang River Basin,aiming to lay a foundation for the further studies on the distribution characteristics of diatom community in the Liujiang River Basin,and also provide the theoretical basis for the utilization and management of water quality.A total of 137 species of epilithic diatoms were identified,belonging to 34 genera 9 families and 6 orders.The diatom richness of each sampling site ranged 13-42 species,with more in wet season than in dry season.There were 5 species and 8 species of dominant species of diatom in dry and wet seasons,with obvious seasonal succession.The cluster analysis showed that there were differences in the spatial and temporal distribution of diatom community structure,which could be divided into 3 groups in dry season,basically located in the upper,middle,lower reaches of the main streams and the tributary sections;but 2 groups in wet season,roughly distributed in the middle-lower reaches and upper reaches of the investigated basin.In dry season,Cyclotella fottii,Cyclotella stelligera,Achnanthes minutissima and Cymbella laveis were found to be the dominant species of the upstream;A.minutissima and Nitzschia valdecostata were more abundant in middle reaches;Navicula cryptocephala,Amphora montana,A.minutissima played a dominant role in the lower reaches.In wet season,the dominant species of the middle and lower reaches were mainly Nitzschia palea;while those in the upstream were A.minutissima,A.montana,Achnanthes petersenii.Based on the principal component analysis(PCA)and redundancy analysis(RDA),the impacts of water quality factors on diatom community were ranked as Pb>Cd>Hg>As>CODMn>DO in dry season,and As>DO>CODMn>NH4+-N>Cd in wet season.The results indicated that Cd,As,DO and CODMn demonstrated an important role in the changes of diatom community structure in different hydrological seasons.Nevertheless,heavy metal parameters showed a greater impact on diatoms in dry season;while the dissolved oxygen had a greater impact on diatoms in wet season.